ros_params.py

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# Author: Patrick Bouffard <bouffard@eecs.berkeley.edu>

import rospy

class ROSParams(object):
    """
    Helper class to be used for grabbing parameters off the parameter server at startup.
    
    Example usage:
    
    from starmac_roslib.ros_params import ROSParams
    
    class MyNodeParams(ROSParams):
        param_defaults = {'param_one': 2.3, 'param_two': 0.0}
        
    class MyNode:
    ...
        def init_params(self):
            self.params = MyNodeParams()
            
        def some_method(self):
            foo = self.params.param_one * 42
    """
    param_defaults = {}
    
    def __init__(self, get_params=True, quiet=False):
        if get_params:
            self.get_params(quiet=quiet)
        
    def get_params(self,quiet=False):
        """
        Loads parameter values from the parameter server, using defaults from self.param_defaults
        Unless the quiet parameter is set, an info message is printed giving the parameter name,
        the set value of the parameter, its type and default value.
        """  
        for param_name, default_value in self.param_defaults.items():
            value = rospy.get_param("~" + param_name, default_value)
            self.__setattr__(param_name,value)
            if not quiet:
                rospy.loginfo('Parameter %s = %s (%s) (default %s)' % 
                              (param_name, 
                               str(value), 
                               str(type(value)), 
                               str(self.param_defaults[param_name])
                               ))